Compared with other painkillers called non-steroidal anti-inflammatory drugs (NSAIDs) and dummy drugs, COX-2 inhibitors caused increases in blood pressure that the authors believe is concerning.

High blood pressure, called hypertension, is a risk factor for stroke and heart attacks.

"Their potential effect on blood pressure elevation requires caution in their use and warrants further investigation," they said.

COX-2 inhibitors have been prescribed as an alternative to NSAIDs because they are gentler on the stomach, carrying a far lower risk of bleeding and ulcers.

But the mounting evidence against COX-2 drugs calls to question whether the entire class will be withdrawn completely.

We'd like the drugs regulators to issue some clear guidelines

A spokeswoman from Arthritis Research Campaign

When safety concerns were raised about another COX-2 inhibitor called celecoxib in December, the UK's Medicines and Healthcare products Regulatory Agency (MHRA) advised patients to make a non-urgent appointment with their GP to have their treatment reviewed.

This advice applied to patients taking Celebrex, Bextra and Arcoxia.

The scientist who first highlighted the concerns about Vioxx, Dr David Graham, says the use of these painkillers should be carefully controlled until there is firm evidence that they are safe.

A spokeswoman from Arthritis Research Campaign said the latest news was alarming, but not over-surprising.

She urged regulators to come to a decision on COX-2 inhibitors.

"If the drugs are not withdrawn, the regulators will have to make sure that people at increased risk of heart attack and stroke are no longer prescribed them.

"We currently have a very unsatisfactory situation where some GPs and hospitals no longer prescribe these drugs to their arthritis patients, yet others are continuing to do so.

"We'd like the drugs regulators to issue some clear guidelines as soon as possible, and end this confusion."

The European Medicines Agency (EMEA), which is due to meet this week, said it would report soon on the COX-2 drugs.